regarding miracle gro:
YES, fertilizer is fertilizer, BUT one big caveat: when you buy miracle grow (which is owned by scott's), your money goes to the 2nd largest investor in GMO technology in the field, second only to monsanto, with whom scott's has a rather cozy relationship (exclusive marketing rights to roundup, acquisition of their lawncare division, etc. etc.).
when you grow in mg you might as well wear a button that reads "i support GMO cannabis". apparently they're already working on it.